An ideal composition for delivery of a topically-active compound to skin or hair delivers the topically-active compound such that it adheres to the skin or hair, while topically-inactive ingredients evaporate or are rinsed from the application site. Delivery of a water-insoluble topically-active compound is facilitated because the topically-active compound is not removed from the application site during the rinsing step. The difficulty with this type of composition resides in incorporating the water-insoluble topically-active compound into an aqueous composition. This difficulty is overcome by forming emulsions. Therefore, topically-active compounds, such as a hair conditioner, a hair dye, a skin care compound or a topical medicament, conventionally have been delivered from either oil-in-water emulsions or water-in-oil emulsions.
With respect to water-soluble and water-dispersible topically-active compounds (hereinafter collectively termed "water-soluble topically-active compounds"), it is easy to incorporate the topically-active compound into an aqueous composition. However, a substantial amount, or all, of the water-soluble compound can be rinsed from the treated skin or hair. The water-soluble compound therefore cannot perform its intended function and is wasted. Accordingly, rinse-off compositions often incorporate an excess of the water-soluble topically-active compound, such that a sufficient amount of the compound remains on the skin or hair after rinsing to perform its intended function. This problem is not encountered with leave-on compositions.
Similarly, two-in-one products, like shampoo-conditioner compositions, have been difficult to formulate not only because of the water solubility of many quaternary ammonium compounds, but also because of the well-known incompatibility between an anionic surfactant and a quaternary ammonium compound. Formulators either have avoided this problem by sequentially contacting the hair first with an anionic surfactant composition, then a quaternary ammonium compound composition, or have overcome this problem by using silicone conditioners in shampoo-conditioners. However, silicones and similar conditioners are water insoluble and an esthetically-unpleasant residue builds up on the hair after repeated applications. In addition, quaternary ammonium compounds impart hair conditioning properties different from a silicone, and therefore it is desirable to condition the hair with quaternary ammonium compounds in place of, or in conjunction with, a silicone.
Investigators therefore have searched for topically-effective compositions that overcome the above-described disadvantages, and that have consumer-acceptable stability and esthetics. Rinse-off, topically-effective compositions however often are difficult to formulate because of the water solubility of the desired topically-active compound. Leave-on, topically effective compositions are difficult to formulate because of the incompatibility between various topically-active compositions.
One type of composition that has been investigated to overcome these problems are multiple emulsions. Multiple emulsions are complex emulsions of emulsions formed by dispersing droplets in a continuous phase, wherein the droplets themselves contain smaller droplets of a liquid similar to the external continuous phase. One type of multiple emulsion is a water-in-oil-in-water emulsion (W.sub.1 -O-W.sub.2), wherein a primary water-in-oil (W.sub.1 /O) emulsion is dispersed in an external aqueous phase (W.sub.2). Multiple emulsions also are known as liquid membrane systems because, in the case of a W.sub.1 -O-W.sub.2 emulsion, an organic membrane, film or layer separates the inner water droplets from the external aqueous phase.
W.sub.1 -O-W.sub.2 multiple emulsion compositions have been used in the pharmaceutical industry as vaccine adjuvants and as sustained release and parental drug delivery systems. However, the low stability of W.sub.1 -O-W.sub.2 multiple emulsion compositions has limited their widespread use.
Multiple emulsion compositions also have been used in cosmetics and skin care products. W.sub.1 -O-W.sub.2 multiple emulsions however were difficult to prepare and were unstable at elevated temperatures. In addition, various active ingredients had a tendency to further destabilize the multiple emulsions, for example causing leakage between the external aqueous phase and internal aqueous phase.
W.sub.1 -O-W.sub.2 multiple emulsion compositions have been disclosed in numerous patents and publications. For example, M. C. Taelman et al., "Multiple Emulsions in Cosmetics", Publication RP112/94E, March, 1994, ICI Europe Limited, Everberg, Belgium, discloses multiple emulsions in general, including methods of manufacturing multiple emulsions. S. Matsumoto et al., J. Dispersion Science and Technology, 10 (1989), pp. 455-482, discloses the use of multiple emulsions in the food, drug and cosmetic industries.
Other publications which disclose multiple W.sub.1 -O-W.sub.2 emulsions are:
S. S. Davis et al., Encyclopedia of Emulsion Technology, Vol. 2; P. Becher, Ed.; Marcel Dekker, Inc., New York, N.Y. (1985), pp. 159-238;
Y. Sela et al., Colloids and Surfaces A: Physicochemical and Engineering Aspects, 83 (1994), pp. 143-150;
K. Oza et al., J. Dispersion Science and Technology, 10(2) (1985), pp. 163-185;
J. Zatz et al., J. Soc. Cosmet. Chem., 39 (May/June 1988), pp. 211-222;
C. Fox, Cosmetics and Toiletries, 101 (Nov. 1986), pp. 101-106 and 109-112;
M. deluca et al., Cosmetics and Toiletries, 105 (Nov. 1990), pp. 65-66 and 69;
T. Tadros, "Application of Multiple Emulsions in Cosmetics", ICI Surfactant publication RP56/92E (1992); and
C. Prybilsky et al., Cosmetics and Toiletries, 106 (Nov. 1991), pp. 97-100.
Various patents disclose multiple emulsion compositions used in cosmetic compositions. For example, WO 94/01073 discloses gelled multiple emulsion compositions for cosmetic use. Other patents include WO 94/02120; WO 93/00160; WO 92/18227; JP 58 183 611; U.S. Pat. No. 5,306,498; and U.S. Pat. No. 4,988,456.
U.S. Pat. Nos. 5,277,899 and 4,963,348, and WO 93/07848, disclose conditioners that have set retention properties. The disclosed compositions are oil-in-water emulsions (O/W), as opposed to the present W.sub.1 /O primary emulsions and the W.sub.1 -O-W.sub.2 multiple emulsion compositions.
Although various patents and publications disclose W.sub.1 -O-W.sub.2 multiple emulsion compositions for cosmetic use, those compositions lack the stability needed for a consumer-acceptable topically-effective composition. The present invention therefore is directed to stable W.sub.1 -O-W.sub.2 multiple emulsion compositions which are capable of depositing water-soluble, topically-active compounds onto hair or skin from compositions, such as hair conditioners, hair shampoos, or skin cleaners.